Merge 3fce612 into 644d427

piccolo/apps/migrations/auto/diffable_table.py

@@ -110,6 +110,8 @@ def __sub__(self, value: DiffableTable) -> TableDelta:
                         column_name=column._meta.name,
                         params=deserialise_params(delta),
                         old_params=old_params,
+                        column_class=column.__class__,
+                        old_column_class=existing_column.__class__,
                     )
                 )
 

piccolo/apps/migrations/auto/migration_manager.py

@@ -252,6 +252,8 @@ def alter_column(
         column_name: str,
         params: t.Dict[str, t.Any],
         old_params: t.Dict[str, t.Any],
+        column_class: t.Optional[t.Type[Column]] = None,
+        old_column_class: t.Optional[t.Type[Column]] = None,
     ):
         """
         All possible alterations aren't currently supported.
@@ -263,6 +265,8 @@ def alter_column(
                 column_name=column_name,
                 params=params,
                 old_params=old_params,
+                column_class=column_class,
+                old_column_class=old_column_class,
             )
         )
 
@@ -328,9 +332,53 @@ async def _run_alter_columns(self, backwards=False):
             _Table: t.Type[Table] = type(table_class_name, (Table,), {})
             _Table._meta.tablename = alter_columns[0].tablename
 
-            for column in alter_columns:
-                params = column.old_params if backwards else column.params
-                column_name = column.column_name
+            for alter_column in alter_columns:
+
+                params = (
+                    alter_column.old_params
+                    if backwards
+                    else alter_column.params
+                )
+
+                old_params = (
+                    alter_column.params
+                    if backwards
+                    else alter_column.old_params
+                )
+
+                ###############################################################
+
+                # Change the column type if possible
+                column_class = (
+                    alter_column.old_column_class
+                    if backwards
+                    else alter_column.column_class
+                )
+                old_column_class = (
+                    alter_column.column_class
+                    if backwards
+                    else alter_column.old_column_class
+                )
+
+                if (old_column_class is not None) and (
+                    column_class is not None
+                ):
+                    if old_column_class != column_class:
+                        old_column = old_column_class(**old_params)
+                        old_column._meta._table = _Table
+                        old_column._meta._name = alter_column.column_name
+
+                        new_column = column_class(**params)
+                        new_column._meta._table = _Table
+                        new_column._meta._name = alter_column.column_name
+
+                        await _Table.alter().set_column_type(
+                            old_column=old_column, new_column=new_column
+                        )
+
+                ###############################################################
+
+                column_name = alter_column.column_name
 
                 null = params.get("null")
                 if null is not None:
@@ -383,7 +431,7 @@ async def _run_alter_columns(self, backwards=False):
                 digits = params.get("digits", ...)
                 if digits is not ...:
                     await _Table.alter().set_digits(
-                        column=column.column_name, digits=digits,
+                        column=alter_column.column_name, digits=digits,
                     ).run()
 
     async def _run_drop_tables(self, backwards=False):

piccolo/apps/migrations/auto/operations.py

@@ -26,6 +26,8 @@ class AlterColumn:
     tablename: str
     params: t.Dict[str, t.Any]
     old_params: t.Dict[str, t.Any]
+    column_class: t.Optional[t.Type[Column]] = None
+    old_column_class: t.Optional[t.Type[Column]] = None
 
 
 @dataclass

piccolo/apps/migrations/auto/schema_differ.py

@@ -308,17 +308,45 @@ def alter_columns(self) -> AlterStatements:
             else:
                 continue
 
-            for i in delta.alter_columns:
-                new_params = serialise_params(i.params)
+            for alter_column in delta.alter_columns:
+                new_params = serialise_params(alter_column.params)
                 extra_imports.extend(new_params.extra_imports)
                 extra_definitions.extend(new_params.extra_definitions)
 
-                old_params = serialise_params(i.old_params)
+                old_params = serialise_params(alter_column.old_params)
                 extra_imports.extend(old_params.extra_imports)
                 extra_definitions.extend(old_params.extra_definitions)
 
+                column_class = (
+                    alter_column.column_class.__name__
+                    if alter_column.column_class
+                    else "None"
+                )
+
+                old_column_class = (
+                    alter_column.old_column_class.__name__
+                    if alter_column.old_column_class
+                    else "None"
+                )
+
+                if alter_column.column_class is not None:
+                    extra_imports.append(
+                        Import(
+                            module=alter_column.column_class.__module__,
+                            target=alter_column.column_class.__name__,
+                        )
+                    )
+
+                if alter_column.old_column_class is not None:
+                    extra_imports.append(
+                        Import(
+                            module=alter_column.old_column_class.__module__,
+                            target=alter_column.old_column_class.__name__,
+                        )
+                    )
+
                 response.append(
-                    f"manager.alter_column(table_class_name='{table.class_name}', tablename='{table.tablename}', column_name='{i.column_name}', params={new_params.params}, old_params={old_params.params})"  # noqa: E501
+                    f"manager.alter_column(table_class_name='{table.class_name}', tablename='{table.tablename}', column_name='{alter_column.column_name}', params={new_params.params}, old_params={old_params.params}, column_class={column_class}, old_column_class={old_column_class})"  # noqa: E501
                 )
 
         return AlterStatements(

piccolo/columns/__init__.py

@@ -1,4 +1,5 @@
 from .column_types import (  # noqa: F401
+    BigInt,
     Boolean,
     Bytea,
     Date,
@@ -14,6 +15,7 @@
     Real,
     Secret,
     Serial,
+    SmallInt,
     Text,
     Timestamp,
     Timestamptz,

piccolo/columns/base.py

@@ -462,15 +462,16 @@ def get_sql_value(self, value: t.Any) -> t.Any:
 
         return output
 
+    @property
+    def column_type(self):
+        return self.__class__.__name__.upper()
+
     @property
     def querystring(self) -> QueryString:
         """
         Used when creating tables.
         """
-        column_type = getattr(
-            self, "column_type", self.__class__.__name__.upper()
-        )
-        query = f'"{self._meta.name}" {column_type}'
+        query = f'"{self._meta.name}" {self.column_type}'
         if self._meta.primary:
             query += " PRIMARY"
         if self._meta.key:

piccolo/query/methods/alter.py

@@ -91,6 +91,24 @@ def querystring(self) -> QueryString:
         return QueryString(f"ALTER COLUMN {self.column_name} DROP DEFAULT")
 
 
+@dataclass
+class SetColumnType(AlterStatement):
+    __slots__ = ("old_column", "new_column")
+
+    old_column: Column
+    new_column: Column
+
+    @property
+    def querystring(self) -> QueryString:
+        if self.new_column._meta._table is None:
+            self.new_column._meta._table = self.old_column._meta.table
+
+        column_name = self.old_column._meta.name
+        return QueryString(
+            f"ALTER COLUMN {column_name} TYPE {self.new_column.column_type}"
+        )
+
+
 @dataclass
 class SetDefault(AlterColumnStatement):
     __slots__ = ("column", "value")
@@ -107,7 +125,7 @@ def querystring(self) -> QueryString:
 
 
 @dataclass
-class Unique(AlterColumnStatement):
+class SetUnique(AlterColumnStatement):
     __slots__ = ("boolean",)
 
     boolean: bool
@@ -129,7 +147,7 @@ def querystring(self) -> QueryString:
 
 
 @dataclass
-class Null(AlterColumnStatement):
+class SetNull(AlterColumnStatement):
     __slots__ = ("boolean",)
 
     boolean: bool
@@ -255,13 +273,14 @@ class Alter(Query):
         "_drop_default",
         "_drop_table",
         "_drop",
-        "_null",
         "_rename_columns",
         "_rename_table",
+        "_set_column_type",
         "_set_default",
         "_set_digits",
         "_set_length",
-        "_unique",
+        "_set_null",
+        "_set_unique",
     )
 
     def __init__(self, table: t.Type[Table]):
@@ -272,13 +291,14 @@ def __init__(self, table: t.Type[Table]):
         self._drop_default: t.List[DropDefault] = []
         self._drop_table: t.Optional[DropTable] = None
         self._drop: t.List[DropColumn] = []
-        self._null: t.List[Null] = []
         self._rename_columns: t.List[RenameColumn] = []
         self._rename_table: t.List[RenameTable] = []
+        self._set_column_type: t.List[SetColumnType] = []
         self._set_default: t.List[SetDefault] = []
         self._set_digits: t.List[SetDigits] = []
         self._set_length: t.List[SetLength] = []
-        self._unique: t.List[Unique] = []
+        self._set_null: t.List[SetNull] = []
+        self._set_unique: t.List[SetUnique] = []
 
     def add_column(self, name: str, column: Column) -> Alter:
         """
@@ -333,6 +353,15 @@ def rename_column(
         self._rename_columns.append(RenameColumn(column, new_name))
         return self
 
+    def set_column_type(self, old_column: Column, new_column: Column) -> Alter:
+        """
+        Change the type of a column.
+        """
+        self._set_column_type.append(
+            SetColumnType(old_column=old_column, new_column=new_column)
+        )
+        return self
+
     def set_default(self, column: Column, value: t.Any) -> Alter:
         """
         Set the default for a column.
@@ -349,7 +378,7 @@ def set_null(
         Band.alter().set_null(Band.name, True)
         Band.alter().set_null('name', True)
         """
-        self._null.append(Null(column, boolean))
+        self._set_null.append(SetNull(column, boolean))
         return self
 
     def set_unique(
@@ -359,7 +388,7 @@ def set_unique(
         Band.alter().set_unique(Band.name, True)
         Band.alter().set_unique('name', True)
         """
-        self._unique.append(Unique(column, boolean))
+        self._set_unique.append(SetUnique(column, boolean))
         return self
 
     def set_length(self, column: t.Union[str, Varchar], length: int) -> Alter:
@@ -472,8 +501,9 @@ def querystrings(self) -> t.Sequence[QueryString]:
                 self._rename_table,
                 self._drop,
                 self._drop_default,
-                self._unique,
-                self._null,
+                self._set_column_type,
+                self._set_unique,
+                self._set_null,
                 self._set_length,
                 self._set_default,
                 self._set_digits,

tests/apps/migrations/auto/test_schema_differ.py

@@ -187,7 +187,7 @@ def test_alter_column_precision(self):
         self.assertTrue(len(schema_differ.alter_columns.statements) == 1)
         self.assertEqual(
             schema_differ.alter_columns.statements[0],
-            "manager.alter_column(table_class_name='Ticket', tablename='ticket', column_name='price', params={'digits': (4, 2)}, old_params={'digits': (5, 2)})",  # noqa
+            "manager.alter_column(table_class_name='Ticket', tablename='ticket', column_name='price', params={'digits': (4, 2)}, old_params={'digits': (5, 2)}, column_class=Numeric, old_column_class=Numeric)",  # noqa
         )
 
     def test_alter_default(self):

tests/table/test_alter.py

@@ -1,6 +1,7 @@
+from piccolo.columns.column_types import Varchar
 from unittest import TestCase
 
-from piccolo.columns import Integer, Numeric
+from piccolo.columns import BigInt, Integer, Numeric
 from piccolo.table import Table
 
 from ..base import DBTestCase, postgres_only
@@ -113,7 +114,6 @@ def test_unique(self):
         self.assertTrue(len(response), 2)
 
 
-# TODO - make it work for SQLite. Should work.
 @postgres_only
 class TestMultiple(DBTestCase):
     """
@@ -137,6 +137,62 @@ def test_multiple(self):
         self.assertTrue("column_b" in column_names)
 
 
+# TODO - test more conversions.
+@postgres_only
+class TestSetColumnType(DBTestCase):
+    def test_integer_to_bigint(self):
+        """
+        Test converting an Integer column to BigInt.
+        """
+        self.insert_row()
+
+        alter_query = Band.alter().set_column_type(
+            old_column=Band.popularity, new_column=BigInt()
+        )
+        alter_query.run_sync()
+
+        query = """
+            SELECT data_type FROM information_schema.columns
+            WHERE table_name = 'band'
+            AND table_catalog = 'piccolo'
+            AND column_name = 'popularity'
+            """
+
+        response = Band.raw(query).run_sync()
+        self.assertEqual(response[0]["data_type"].upper(), "BIGINT")
+
+        popularity = (
+            Band.select(Band.popularity).first().run_sync()["popularity"]
+        )
+        self.assertEqual(popularity, 1000)
+
+    def test_integer_to_varchar(self):
+        """
+        Test converting an Integer column to Varchar.
+        """
+        self.insert_row()
+
+        alter_query = Band.alter().set_column_type(
+            old_column=Band.popularity, new_column=Varchar()
+        )
+        alter_query.run_sync()
+
+        query = """
+            SELECT data_type FROM information_schema.columns
+            WHERE table_name = 'band'
+            AND table_catalog = 'piccolo'
+            AND column_name = 'popularity'
+            """
+
+        response = Band.raw(query).run_sync()
+        self.assertEqual(response[0]["data_type"].upper(), "CHARACTER VARYING")
+
+        popularity = (
+            Band.select(Band.popularity).first().run_sync()["popularity"]
+        )
+        self.assertEqual(popularity, "1000")
+
+
 @postgres_only
 class TestSetNull(DBTestCase):
     def test_set_null(self):